Recently, Patent Foramen Ovale (hereafter referred to as PFO) is noted as cardiogenic cause of stroke or migraine. PFO is a symptom of still opening a patent foramen ovale, which provides left-to-right blood shunt in a heart in infancy, even after grownup to an adult, and from 20 to 30% of adults are said to have.
A patent foramen ovale generates at a septum secundum of a heart, and is occluded by a septum primum in a usual heart, due to higher left atrial pressure than right atrial pressure, however, in tension (for example in coughing or holding on), higher right atrial pressure than left atrial pressure results in opening of a septum primum toward a left atrial side, and blood flowing from a right atrial side (a vein side) to a left atrial side (an arterial side). In the case where blood clots are contained in this blood, the blood clots result in to move from a vein side to an arterial side, and flow in a direction of a left atrial→a left ventricle→an aorta→a brain, thus causing stroke or migraine.
As treatments for such diseases, a drug therapy (aspirin, warfarin), a closing operation of a patent foramen ovale by percutaneous catheter technique, and an open-heart operation by extracorporeal circulation are included. The drug therapy is a first choice treatment, however, has a problem that control of administration amount is difficult and cessation of bleeding is difficult during administration. The percutaneous catheter technique and the open-heart operation accompany invasion, however, possibility of relapse is none due to being a radical operation. At a present stage, as for an occlusion technique, the open-heart operation is considered to be surer, however, in consideration of also risk in carrying out extracorporeal circulation, and large area of invasion in skin incision, treatment by percutaneous catheter technique is a desirable method as long as similar effect as by the open-heart operation can be obtained.
A device for the closing technique using a percutaneous catheter can also be used in closing a passage-like defect such as a congenital type of atrial septal defect (ASD), PFO, ventricular septal defect (VSD), and patent ductus arteriosus (PDA), and the following ones are included as such a device.
For example, to close a defect, one for sandwiching a disk-like membrane by indwelling at each of a left atrial side and a right atrial side (see abstract, paragraphs 0022 and 0023, and FIG. 1 of JP-A-2002-355248; see paragraph 0010, and FIG. 2 of JP-A-2002-248105; see abstract, paragraphs 0035 and 0036, and FIG. 1 of JP-A-2002-119516; see abstract and FIG. 1 of US-2003-195530A; and see abstract of U.S. Pat. No. 6,174,322); one for sandwiching by using an anchoring member formed by a wire rod at one end, and a disk-like membrane at the other end (see paragraphs 0037 and 0042, and FIGS. 11, 11A and 11C of JP-2004-528131A); or one for sandwiching by using an anchoring member formed by wire rods at both ends (see abstract and FIG. 4 of US-2003-225421A); or the like.
However, use of a pair of disk-like membranes make a structure complicated and increases area of a foreign material, which tends to easy adherence of blood clots; in particular, adherence of blood clots onto a disk-like membrane at the left atrial side could cause stroke by flowing thereof, and could break a septum primum having thin thickness.
Use of a disk-like membrane member or an anchor member made of a wire material also raises a problem, in the case of a indwelling and sandwiching system onto each of the left atrial side and the right atrial side, of generation risk of displacement due to non-fixed position thereof, and being not a structure for surely retaining thereof at the predetermined position.
In addition, the above-described device is delivered and indwelled from a vein of a femoral region to inside the cardiovascular, and a delivery apparatus is used to carry out delivery and release of such a device. A delivery apparatus usually uses a catheter for storing a device inside the catheter, and releasing a device after delivery to the predetermined position.
Conventional delivery apparatuses carry out a device release by using a screw mechanism, which exerts force on a device itself at device releasing, resulting in displacement of indwelling position, or deformation of tissue of a part for mounting, or could deviate the device to the left atrial side, and thus a sure and safe indwelling state could not be obtained in some cases.